We propose, theoretically analyze and experimentally demonstrate a novel broadband operating Si-nanowire multistagedelayed Mach-Zehnder interferometer (DMZI) based (De)MUXs utilizing wavelength insensitive couplers (WINCs) andthe discrete phase shifters for the phase matching between cascade-connected DMZIs. Based on the coupled mode theoryand transfer matrix method, the coupling characteristics of a Si-wire directional coupler (DC) and WINC are analyticallydiscussed from the viewpoint of a wavelength sensitivity of coupling efficiency [κ_(Coup)(λ)]. We theoretically verify thatthe operating window of the proposed DeMUX can be as broad as >110 nm by introducing the WINC and the additionalphase matching between multiple DMZIs. Based on the theoretical analysis, 300-mm waferscale ArF-immersionlithography process are used to fabricate the Si-wire-based 1×4Ch DeMUXs. It will be shown that >110-nm-wideoperating window for the proposed DeMUXs with four kinds of channel spacings (Δν=400, 800, 1250, 1900GHz). Thetheoretically identified aspect of nearly constant κ_(Coup)(λ) by the WINC and the phase matching by the phase shifter isproven to be extremely effective way to make the production yield much better, because DeMUX spectral responsekeeps nearly constant even if insufficient fabrication accuracy makes spectral response be shifted toward longer orshorter wavelength side. In addition, it will be shown that operating spectral window could be made much wider byoptimizing the WINC design parameters in the DeMUX configuration. The proposed scheme would be attractive forincreasing available channel count without inducing any excessive losses, which makes the proposed scheme morepractical in WDM optical transceivers.
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